Process for manufacturing electrodes



HANS BARDT, O11

sanrreeo, c'nrnn, ssslenon 'ro soomnen nrnn rnnrenunercn, or snn'rreeo, ems, A. coone'rron or omen.

ERGCESS FOR- hiBtNUEACT'URIN'G K0 Drawing.

To all whom it may concern:

Be it known that 1, Hints BAnn'r, citizen of Germany, residing at Santiago, Chile, have invented certain new-andvuseful Imrovements in Processes for Manufacturing lectrodes, of which the following is e. specification.

The present invention relates to improvements in the manufacture of electrodes for electrolytic processes, in which peroxide of manganese or peroxide of lead has been.

used.

Upto the present, anodes of peroxide of manganese in a compact form have been made for electrolytic purposes by decomposing nitrate of manganese at a certain fixed temperature. Electrodes of this description, however, possess'but "a relatively small degree of conductivity, owing to the presence therein of considerable quantities of non-conducting manganese dioxide in an amorphous state, produced during the above procedure, and which is enveloped by the crystalline modification of manganese dioxide.

Another reason for the low conductivity of these electrodes is that during the process of decomposing nitrate of manganese, a great number of cavities form in the me;

terial, with the result that the electrodes are not produced in a completely compact state. Peroxide of lead anodes for electrolytic purposes were manufactured up to the present time, by electrolytically oxidizing, within a bath of sulphuric acid, lead oxide placed on grid plates in layers by means of a binding substance, thereby following the method generally employed in the manufacture of storage batteries. The life of this type of anode, when used for electrolytic purposes, is very short owing to the loose (porous state of the layers of peroxide of lea Attempts were also made in the direction of electrodepositing peroxide of lead onto,

a suitable insoluble anode, using iron wire or a carbon-rod as'anode material, a solu-' tion of nitrate of lead being the electrolyte.

With this procedure, however, metallic lead is deposited at the same time, atthe cathode, forming oblong needles and leaves .which must be continually removed as,

otherwise, frequent short-circuits are caused thereby. Moreover, it is necessary to continually keep the acidity of the electrolyte as low as possible, maintaining its satura- Spccification of Letters l atentc Application filed September 17, 1921.

Patented July is, race.

serial Ito. sol lac.

I tion by periodically adding lead oxide. A

particularly troublesome feature of this procedure, however, is presented by the necessity offinally removing, by drilling or otherwise, the core (consisting, for instance,

as in the above example, of iron wire era carbon-rod),' as otherwise the layer or peroxide of lead is thrown off. This is caused by nitrate being enclosed within the peroxide, the metal core or the carbon, re-

spectively, forming a strong couple together with the peroxide layer, which latter is ushcd from its supports. The. removal,

owever, of the primary core by drilling or otherwise, leaves the peroxide layer in an extremely fragile condition and exposed to 111311110115 influences. Due to all these circumstances, it has been found impossible u to the present time to manufacture peroxi e' oflead anodes in the form of plates.

It has also been proposed to impregnate up the pores and thereby to render possible the .manufacture' of faultless electrodes. This procedure, however, has not met with any success; furthermore, it only serves to com licate operations and to increase the pro uction costs considerably.

Now, it has been proved by extensive, experiments that it is possible to manufacture, by anodic deposition, electrodes of peroxide of manganese or of lead in 3; perfectly compact condition and with a high degree of tubes, without any necessity forremoving the carbon rods with a suitable material before depositing the peroxide in order to fill fill the peroxide-holders after the peroxide has beendeposited thereon, nor is the peroxide layer destroyed by any processes locally taking place within the electrode.

It has further been observed that peroxide electrodes having an extraordinarily large surface can be'produced provided that, after a smooth and compact peroxide layer has been formed, the anode is charged with current of a density being a multiple of the 1 and an excess of density originally employed, and that the electrolyte contains a high percentage of free perchloric acid. Under these conditions, the electrode surface assumes a honey-combed appearance.

The following example may serve as an illustration In one litre of a 20 per cent perchloric acid solution, about 90 grammes of carbonate of manganese are dissolved, or an equivalent, such as lead oxide, in which case about 150 grammes of lead oxide are used. The solution thus obtained is electrolyzed at the temperature of the laboratory, using magnetic oxide of iron or ferro-silicon as anode material, and copper or lead-plate as cathodes. To commence with, a current density of 0.3 to 0.5 amperes er square decimetre of anode area is emp oyed. As soon hs a compact, uniform and thin peroxide film is deposited on'the anode-surface, the current density of the anode is increased up to 2.5 to 3 amperes and then the electrolytic process is continued for a further period of time, according to the thickness of the peroxide layer which it is desired to produce.

In the same proportion as the electrolyte is impoverished during the operation in manganese or lead, respectively, fresh carbonate of manganese or lead oxide is con tinually introduced. I claim: p

1. Process for the manufacture of electrodes, which consists in electrolyzing a solution containing carbonate of manganese perchloric acid, and employing anode material inert with respect to perchloric acid whereby a deposit of a peroxide film is formed upon the anode to serve as the desired electrode. v

2. Process for the manufacture of -electrodes, which agers in electrolyz" a solution containing carbonate of manganese and an excess of percholoric acid, and employing anode material inert with respect to perchloric acid, subjecting the mixture to a low current density, and after the formation of a thin peroxide film on the anode surface, increasing the current density over that. first used whereby an increased thickness of the peroxide deposit is obtained and the completion of the electrode is effected.

3. Process for the manufacture of electrodes, which consists in electrolyzing a solution containing carbonate of manganese and an excess of perchloric acid, and employing anode material inert with respect to perchloric acid, subjecting the mixture to a current density of approximately 0.42 amperes per square decimeter of anode area, and after the formation of a thin peroxide film on the anode surface, increasing the current density to approximately 2.5 to 3 amperes thereby increasing the anode deposit and completing the desired electrode.

In a process for the manufacture of electrodes, the steps which consist in electrolyzing a solution containing carbonate of manganese and an excess of perchloric acid and employing anode material inert with respect to perchloric acid, subjecting the mixture to a current density of approxiniately 0.4 amperes per square decimeter of anode area; after the formation of a thin peroxide film on the anode surface, increasing the current density to approximately 2.5

to 3 amperes, and adding additional carbonate of manganese as electrolyzation takes place.

In testimony whereof I afix m siature.

HANS A m. Witnesses WALTER J. Tuscan,- AL ARMEKER. 

